Here is a picture that was included with the plans of the part I am working on now. Maybe it will help you visualize the bends and twists. This is not my transom, just hopefully what it will look like when I finish this part of the task. Then after the side pieces are in, it gets two battens which go around the back from side to side. One will be at the very bottom and the other about half way up. The transom knees have been notched for the battens.

Steve..... I am satisfied with the plans but, as I have said, everything is there and you have to look for it. As far as the transom goes, the plans are somewhat lacking. I had to use a CAD program to figure out the radius on two different parts. I was also missing a couple critical measurements. After two email exchanges, I did receive some clarification. One thing that would really be helpful is a list of materials like Glen-L gives you with their plans. Some instructions would be nice as well. To sum it up, a very nice and very strong boat can be built with these plans, but for a "first build", I would stick with Glen-L

I spent about two hours this morning fitting the port transom side curved piece. I took a little off here and a little off there until it fit nicely where it belongs... It is very hard to clamp it in place because of the curves. So now I have to do the starboard side and then figure out how to finish sand each one with a twist from top to bottom. The outside side radius is correct so that won't require any sanding. I'm thinking to glue it all together and then attack the whole thing with a belt sander until it is right. I have time to try to come up with a better way.

I don't know where you might think it is concave. If you look at the profile from front to back, the outside radius is correct. If you look at it from the side, you can see how it has to be sanded with a twist from the curved top piece to match the straight bottom piece. I think you could have come up with a much simpler design Ken

Nice job, lots of custom tweaking.
What I find interesting is it would have been so much easier if there was a bottom curved/bowed member between the transom and the bottom, it would have followed the same curve of the top member, just longer. It would have meant minimal twist in the port and starboard curved pieces you are now fitting. And it would have been structurally more sound as it would back up the intersection of the transom planking and bottom planking with something other than a 1/2" or so batten on edge. Look at the Monaco and Riviera transoms and see how those are put together for comparison. Or even the Chris Craft Barrelbacks. I have to wonder, is what you have the original Nelson Zimmer designed structure or is it the CAD guy's (mis) interpretation? Woodenboat Magazine sells plans for this boat too, no patterns and you loft it yourself. I'm curious to see how they compare?

Murphy's Law: Anything that can go wrong, will go wrong.
Griffin's Law: Murphy was an optimist.

Peter, I think the plans are a combination of the original drawings brought somewhat up to date with CAD programs. I have looked at the plans from Wooden Boat and they look very much the same. Just they do require lofting which I am not into.... As far as strength of the transom goes, the side to side battens are almost 3/4" thick material, laminated in three 1/4" pieces. Also the keel, stringers, and the bottom battens do attach to the bottom transom side to side batten which will make it very strong, I think. The method you suggested would also work and probably would have been a lot less complicated.